数据结构串的基本操作及KMP算法

将串的基本操作C语言实现，实现KMP算法算出NEXT函数和NEXTVAL的值。

SqString.h的基本内容

typedef int Status;typedef struct{    unsigned char data[MAXSTRLEN+1];    int length;}SString;Status StrInput(SString &S);void StrAssign(SString &s,char cstr[]);Status StrOutput(SString S);Status Concat(SString &T, SString S1, SString S2);Status SubString(SString &Sub, SString S, int pos, int len);Status GetStrLength(SString S);Status ClearStr(SString &S);Status StrIsEmpty(SString S);Status StrCopy(SString &T, SString S);Status StrIndex(SString S, SString T, int pos);bool StrCompare(SString S, SString T);Status StrInsert(SString &S, int pos, SString T);Status StrDelete(SString &S, int pos, int len);Status DestroyStr(SString &S);void get_next(SString S, int *next);int KMP(SString S, SString T, int pos);

函数具体实现

① 初始化串（本文给了两种方法）
将所给字符串放入串S中或者从键盘输入字符串

void StrAssign(SString &s,char cstr[]){    int i;    for (i=1;cstr[i-1]!='\0';i++)        s.data[i]=cstr[i-1];    s.length=i-1;}Status StrInput(SString &S){    printf("请输入要输入的数量：\n");    int n;    scanf("%d",&n);    int i;    printf("请输入%d个字符：\n");    getchar();    for(i=0;i<n;i++)        scanf("%c",&S.data[i+1]);        S.length=n;    return OK;}

② 字符串的输出

//字符串的输出Status StrOutput(SString S){    int i;    for(i=1;i<=S.length;i++)        printf("%2c ",S.data[i]);    printf("\n");    return OK;}//  符串的拼接Status Concat(SString &T, SString S1, SString S2){    int i;    bool uncut;    if (S1.length + S2.length <= MAXSTRLEN)    {        for (i = 0; i <= S1.length; i++)            T.data[i] = S1.data[i];        for (i = S1.length + 1; i <= S1.length + S2.length; i++)            T.data[i] = S2.data[i - S1.length];        T.length = S1.length + S2.length;        uncut = TRUE;    }    else if (S1.length<MAXSTRLEN)    {        for (i = 0; i <= S1.length; i++)            T.data[i] = S1.data[i];        for (i = S1.length + 1; i <= MAXSTRLEN; i++)            T.data[i] = S2.data[i - S1.length];        T.length = MAXSTRLEN;        uncut = FALSE;    }    else    {        for (i = 0; i <= MAXSTRLEN; i++)            T.data[i] = S1.data[i];        uncut = FALSE;    }    return uncut;}//  返回需要的子字符串Status SubString(SString &Sub, SString S, int pos, int len){    int i;    if (pos<1 || pos>S.length || len<0 || len>S.length - pos + 1)        return ERROR;    for (i = 1; i <= len; i++)        Sub.data[i] = S.data[pos + i - 1];    Sub.length = len;    return OK;}//  询长度Status GetStrLength(SString S){    return S.length;}//  清除串Status ClearStr(SString &S){    int i;    for (i = 1; i <= S.length; i++)        S.data[i] = '\0';    S.length = 0;    return OK;}//  判断串是否为空Status StrIsEmpty(SString S){    if (S.length = 0)        return 1;    else        return ERROR;}//  将串S复制给TStatus StrCopy(SString &T, SString S){    int i;    for (i = 0; i <= S.length; i++)    {        T.data[i] = S.data[i];    }    return OK;}//  搞复杂度查询子串Status StrIndex(SString S, SString T, int pos){    int i=pos+1,j=1;    while(i<=S.length&&j<=T.length)    {        if(S.data[i]==T.data[j])        {            ++i;++j;        }        else        {            i=i-j+2;j=1;        }    }    if(j>T.length)return i-T.length;    else return FALSE;}//判断串是否相等bool StrCompare(SString S, SString T){    bool cmp=TRUE;;    if (T.length != S.length)        cmp=FALSE;    else    {        int i;        for(i=1;i<=T.length;i++)        {            if(T.data[i]!=S.data[i])            {                cmp=FALSE;break;            }        }    }    return cmp;}//串的插入Status StrInsert(SString &S, int pos, SString T){    int i;    if (S.length + T.length > MAXSTRLEN || pos<=0 || pos>S.length)        return ERROR;    for (i = T.length + S.length; i >= S.length; i--)        S.data[i] = S.data[i - T.length];    for (i = 1; i <= T.length; i++)        S.data[pos+i-1] = T.data[i];    S.length+=T.length;    return OK;}//串的删除Status StrDelete(SString &S, int pos, int len){    int i;    if (pos<1 || pos>S.length || len<0 || len>S.length - pos + 1)        return ERROR;    for (i = pos; i <= pos+len; i++)        S.data[i] = S.data[i + 1];    S.length = S.length - len;    return OK;}//销毁串Status DestroyStr(SString &S){    int i;    for (i = MAXSTRLEN; i >= 0; i--)        free(S.data + i);    return OK;}

KMP算法部分，包括next函数和修正的nextval函数

void get_next(SString S, int *next){    int i=1,j=0;    next[1] = 0;    while (i < S.length)    {        if (j == 0 || S.data[i] == S.data[j])        {            ++i;            ++j;            next[i] = j;        }        else{            j = next[j];        }    }    for(i=1;i<=S.length;i++)        printf("%2d ",next[i]);}void get_nextval(SString T,int *nextval){    int i=1;nextval[1]=0;    int j=0;    while(i<T.length)    {        if(j==0||T.data[i]==T.data[j])        {            ++i;++j;            if(T.data[i]!=T.data[j])nextval[i]=j;            else nextval[i]=nextval[j];        }        else j=nextval[j];    }    for(i=1;i<=T.length;i++)        printf("%2d ",nextval[i]);}int KMP(SString S,SString T,int pos){    int i = pos;    int j = 1;    int next[MAXSTRLEN];    get_next(T, next);    while (i <= S.length && j <= T.length){        if (j == 1 || S.data[i] == T.data[j]){            ++i;            ++j;        }        else{            j = next[j];        }    }    if (j>T.length)        return i - T.length;    else return 0;}int KMPval(SString S,SString T,int pos){    int i = pos;    int j = 1;    int nextval[MAXSTRLEN];    get_nextval(T, nextval);    while (i <= S.length && j <= T.length){        if (j == 0 || S.data[i] == T.data[j]){            ++i;            ++j;        }        else{            j = nextval[j];        }    }    if (j>T.length){        return i - T.length;    }    else return 0;}

主函数部分：

int main(int argc, char* argv[]){    int j,pos=0;    SString S,T;    printf("----------------------------------------------------------\n");    StrAssign(S,"ILOVEGOOGLENOW!");    StrAssign(T,"GOOGLE");    printf("S为:\n");StrOutput(S);    printf("串S长度 %d  ",GetStrLength(S));    printf("\n");    printf("T为:\n");StrOutput(T);    printf("串S长度 %d  ",GetStrLength(T));    printf("\n");    printf("----------------------------------------------------------\n");    printf("简单匹配算法:\n");    printf("t在s中的位置=%d\n",StrIndex(S,T,0));    printf("----------------------------------------------------------\n");    printf("   T    ");    StrOutput(T);    printf(" next   ");KMP(S,T,0);    printf("\n");    printf(" nextval");KMPval(S,T,0);    printf("\n");    printf("----------------------------------------------------------\n");    printf("KMP算法:\nnext的值  ");    printf("  \nt在s中的位置=%d\n",KMP(S,T,0));    printf("----------------------------------------------------------\n");    printf("修正KMP算法:\nnextval的值");    printf("  \nt在s中的位置=%d\n",KMPval(S,T,0));    printf("----------------------------------------------------------\n");    return 0;}

总结：

1. 由于数组是unsigned char类型，如果像书上把S[0]存储数组长度不妥，类型不匹配，建议不使用，建议使用改进的结构体SString类型。
2. 注意每个函数实现时，S.data[0]不作为存储，应该从1开始。
   欢迎关注我的博客：omegaxyz.com